1. Field of Invention
The present invention pertains to an improved process for preparing alkanones and alkanols. In particular, the present invention involves the steps of oxidizing an alkane and/or alkene having from 3 to 30 carbon atoms to form an oxidation mixture containing alkylhydroperoxide, adding a basic aqueous solution to the oxidation mixture, and decomposing the alkylhydroperoxide in the presence of a heterogeneous decomposition catalyst.
2. Description of Related Art
A process for preparing cyclohexanone and cyclohexanol is described in U.S. Pat. No. 4,543,427 issued to Hartig et al. According to the Hartig patent, cyclohexane is first oxidized with air or oxygen to produce an oxidation mixture containing cyclohexyl hydroperoxide. The cyclohexyl hydroperoxide is subsequently decomposed into cyclohexanone and cyclohexanol. The decomposition is effected in the presence of a heterogeneous decomposition catalyst consisting of cobalt immobilized on a zeolite carrier. This decomposition catalyst is said to have a longer life and greater resistance to acids and water than metal-on-carrier catalysts known in the art, such as cobalt on active aluminum oxide, silica gel, or carbon, as described in U.S. Pat. No. 2,851,496 issued to Cates et al.
One disadvantage of the above-mentioned process is that it employs a zeolite as carrier material. Unfortunately, the zeolite is very difficult to obtain. Another disadvantage is that a decrease in the catalyst activity is generally observed. That is, a small amount of cobalt from the cobalt-on-zeolite decomposition catalyst dissolves in the reaction mixture, resulting in limited catalyst life. A further disadvantage is that the presence of a separate water phase during the decomposition of the alkylhydroperoxides further diminishes the catalyst activity by encouraging the cobalt to dissolve in the reaction mixture. The separate water phase thereby causes a significant decrease in the activity of the decomposition catalyst over a short period of time (e.g., a few hours). The separate water phase forms as a byproduct in the oxidation reaction of the cyclohexane and in the decomposition reaction. The negative effect of a separate water phase on the life of a heterogeneous decomposition catalyst is also described in, for instance, U.S. Pat. No. 4,042,630 issued to Wolters et al.
Wolters et al. purports to overcome the problems associated with the Hartig patent by providing a process wherein the formation of a separate water phase is prevented during the decomposition of a cycloalkylhydroperoxide by continuously stripping the oxidation mixture with a stripping gas. The water concentration is preferably maintained at or below a saturation concentration. This stripping process, however, exhibits several distinct disadvantages. First, the stripping process requires a complex decomposition reactor for enabling decomposition and stripping to occur simultaneously and an elaborate apparatus for recirculating the stripping gas. In addition, the effect of the stripping step is not isolated to removing unwanted water. Instead, cyclohexane and reaction products such as cyclohexanol and cyclohexanone are undesirably stripped from the oxidation mixture by the stripping gas. Costly additional processing steps are often required to recover these valuable compounds.